Montana Department of Transportation


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Public Involvement

Armington Junction Roundabout

Armington Junction Roundabout project logo

Project Overview

The Montana Department of Transportation has proposed construction of a roundabout at the junction of US 87/89 near Belt, MT, commonly known as Armington Junction. This proposed roundabout is part of the Belt North and South Phase 3 project. Because MDT’s top priority is the safety of all roadway users the intersection has been designed as a large-diameter, single-lane roundabout in order to provide significant reductions in crashes while providing considerations and space for large trucks and special vehicles commonly traveling the roadway.

Project Timeline and Cost

The Armington Junction Roundabout is the third phase of the Belt North and South Project which extends from the bottom of Belt Hill to Armington Junction. Phases 1 and 2 have been constructed, with third phase construction awaiting final design of the roundabout intersection improvement.

Full cost of the Belt North and South Project which included bridge replacement, road construction, and the current roundabout in development is anticipated to be between $15-20M.

The cost of the intersection includes realignment of current roads to meet safety and design standards with wider roadways, while also providing improved safety features for non-motorized travelers. The total cost of the intersection will be approximately $3.1 million. Construction is estimated to begin in 2021.

Simple. Successful. Safe.

Through careful planning, roundabouts are designed to substantially reduce the types of crashes which result in serious injuries or fatalities. Roundabouts constructed at intersections along high-speed, two-lane rural highways reduce crashes by 68% and reduce serious injury crashes by up to 88%.

Roundabouts also improve traffic flow and reduce the amount of time you have to wait to go through the intersection. Instead of coming to a complete stop, as you would at a signal or sign, traffic slows, you yield to traffic in the circle to left, then enter the roundabout. Roundabouts are also easy for pedestrians to navigate, as they only have to cross one direction of traffic at a time.

A roundabout in Helena at the intersection of Canyon Ferry Road and Lake Helena Drive reduced crashes by 70% and eliminated fatalities over a five-year period.

Made with Travelers in Mind

Roundabouts are constructed with large trucks, RVs, equipment, and horse trailers in mind. The interior section of the roundabout containing colored and patterned concrete is called a truck apron and these larger vehicles are encouraged to use the truck apron to be able to safely drive through the roundabout.

Large Loads

  • Designed to accommodate the turning movements of large trucks.
  • Roundabout design and size influenced by truck turning paths.

Mountable Truck Apron

  • Trucks can track onto mountable apron.
  • Designed with flat slope and low height to accommodate low clearance vehicles.
  • Sufficient width for trailer turning paths.
Armington Junction Roundabout Project roll plot

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